In the United States, it's estimated that about 7 million people are living with Alzheimer's disease and related dementias. But the number of people with a formal diagnosis is far less than that.
Erin Abner, PhD, an epidemiologist at the University of Kentucky, said the results were not surprising and that there are many barriers to diagnosis.
"Where we live is a powerful influence on our brain health," she said. "It is very difficult for adults in many parts of the country to access behavioral neurological specialist care — in many cases waiting lists to be seen are months or even years long."